path fixing PPC bootstrap

[Richard Sandiford]

Vladimir Makarov <vmakarov@redhat.com> writes:
> Mike Meissner pointed me out that my last patch broke PPC bootstrap.  I 
> submitted a quick fix for it and now I am sending the path after 
> bootstrap on ppc is done successfully.
>
> Sorry for the inconvinience.
>
> 2014-11-25  Vladimir Makarov  <vmakarov@redhat.com>
>
>          * ira-lives.c (process_bb_node_lives): Make code with conditional
>          REAL_PIC_OFFSET_TABLE_REGNUM.

REAL_PIC_OFFSET_TABLE_REGNUM is really an i386-local thing though.
There's no documentation for it in tm.texi and this is the first
use of it in generic code.

I suppose I'm just being lazy and not building and trying it out
for myself, but could you describe the original fix a bit more?
The comment says:

	  /* Processing insn usage in call insn can create conflict
	     with pic pseudo and pic hard reg and that is wrong.
	     Check this situation and fix it at the end of the insn
	     processing.  */

but where does the conflict come from?

Thanks,
Richard